The present invention is related to the field of tissue welding, and more specifically to a device and method for automating tissue welding in a living body.
Tissue closure is most commonly performed using sutures, which are inexpensive, reliable, and readily available. Unfortunately, sutures cause additional tissue damage during their placement and tying. Sutures also result in the introduction of a foreign material into the body, increasing the risk for further damage or rejection. Moreover, sutures do not necessarily result in a water tight seal and may require a long healing time.
The placement of sutures involves a complicated set of movements that may be difficult of impossible in microsurgical or minimally invasive applications. Other mechanical methods such as staples or clips have the advantage of being uniform but the disadvantage of inflexibility, and the same basic limitations apply.
Laser tissue welding is the procedure of using focused laser energy to bond tissues together. The absorbed energy results in a molecular alteration of the affected tissue and causes bonds to form between neighboring tissues. Laser soldering is a method of improving tissue welding by introducing a proteinaceous solder material between the tissue or other surfaces to be joined prior to exposure to the laser. Soldering is beneficial for its ability to enhance bond strength, lessen collateral damage, and enlarge the parameter window for a successful bond. The solder is able to do this by holding the tissues together creating a larger bonding surface area, sometimes by as much as two degrees of magnitude.
Laser tissue welding has been used successfully in nerve, skin, and arterial applications. The technique offers significant advantages for securing and sealing skin grafts, repairing solid-tissue organ damage, minimizing laceration trauma, and closing surgical incisions. A major advantage of tissue welding is the instant tissue healing and sealing that it offers, which allows for a quicker return to functional recovery.
Tissue welding typically uses an 800 nm-range laser in conjunction with a chromophore (e.g., indocyanine green (ICG)) to essentially heat, denature and fuse together skin and organ tissues. In a representative method, a solution of albumin and ICG is applied to a wound site. While skin, blood and other bodily tissues have low absorption coefficients in the infrared and near-infrared range, ICG has an absorbance peak at 800 nm. The thermal energy emitted by the laser is thereby confined to the ICG, adjacent albumin applied at the weld site, and the immediately surrounding area. During irradiation, collagen fibers in the tissue deform under thermal stress and form new couplings at the molecular level.
Current tissue welding techniques are highly dependent on the individual skill and technique of the operating surgeon. Laser tissue welding processes require the surgeon to determine the appropriate dose of laser energy, then manually apply irradiation by directly manipulating an optical fiber handpiece. Accurate determination of optimal laser parameters is difficult in this system. Furthermore, manual control of laser positioning and movement can, and often does, lead to under or overexposure of tissues to laser energy, which can cause failed welds and tissue death, respectively.
The success of tissue welding techniques can vary greatly due to manual laser control. The variation in technique among surgeons makes accurate research difficult, if not impossible, and the lack of standardized irradiation patterns and dosages only adds to the inconsistency of tissue welding procedural success. For laser welding to reach its full potential, it must become a more consistent and repeatable process.